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Effect of shielding gas on welding performance and properties of duplex and superduplex stainless steel welds

Abstract

The influence of shielding gases on welding performance and on properties of duplex and superduplex stainless steel welds was studied. Using argon as the reference gas, helium, nitrogen and carbon dioxide were added and five mixtures evaluated. Bead-on-plate welds and circumferential pipe welds were produced using mechanised GMA welding in the downhand position. Welding performance, corrosion resistance, mechanical properties, microstructural features and weld imperfections were assessed and related to the shielding gas. Shielding gases containing 30 % helium showed excellent results; whilst pure argon showed unstable arc and poor weld pool fluidity and Ar + 2 %CO2 resulted in underfill and porosity. Mixtures containing helium resulted in higher ductility welds and higher impact toughness values than welds produced with Ar + 2 %CO2. Sound and balanced duplex microstructures free from intermetallics were found with suitable ferrite contents for all the shielding gases studied. All the duplex pipe welds passed the corrosion test regardless of the shielding gas used, and the best results in the corrosion test for superduplex pipe welds were found when using Ar + 30 %He + 0.5 %CO2 + 1.8 %N2 as shielding gas.

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Acknowledgments

The Knowledge Foundation is gratefully acknowledged for the economic funding. The great support received from the business partners involved: AGA Gas AB, ESAB AB and Sandvik Materials Technology and the involvement and contribution of their representatives are also acknowledged.

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Correspondence to M.A. Valiente Bermejo.

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Doc. IIW-2511, recommended for publication by Commission IX “Behaviour of Metals Subjected to Welding.”

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Valiente Bermejo, M., Karlsson, L., Svensson, LE. et al. Effect of shielding gas on welding performance and properties of duplex and superduplex stainless steel welds. Weld World 59, 239–249 (2015). https://doi.org/10.1007/s40194-014-0199-7

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  • DOI: https://doi.org/10.1007/s40194-014-0199-7

Keywords

  • Duplex stainless steels
  • Welding
  • GMA welding
  • Shielding gases